Finally we can ask what happens when we consider all four gap genes together, as in Fig REF . We know that in total there is more than four bits of positional information available, so that gap gene expression levels specify nuclear positions with \(\sim \) 1% accuracy along the length of the emrbyo [1]}. We can capture a large fraction of this information by keeping only four bits of information about the expression levels, or just one bit per gene (Fig REF B). But even this is not the same as reading expression level individually to one bit precision, since the optimal use of these four bits is to encode combinations of expressions levels, as in the case of two genes in Fig REF .
